20 



BULLETIN 278, U. S. DEPARTMENT OF AGRICULTURE. 



Other arsenicals, namely, commercial arsenite of zinc and commercial 

 arsenate of calcium, were likewise tested. The results are given in 

 Table XL 



Table XI. — Tests of the killing effect of various materials on the fall webuorm. 

 [Experiment started July 17, 1914, Benton Harbor, Mich.; 10 larvee in each lot.] 





Name and dilution. 



Dates of exami- 

 nation and num- 

 ber of larvae 

 dying in each lot. 



cl 



o 



•a 



,2 



a 



3 



"3 

 o 

 Eh 



•a 



<u 



a 



cr 

 o 



ll 



•o o 

 a 



a 



3 



p 



be 



.2 

 "3 

 •a 



sa 



o 



* 



1-i 



July. 



August. 



a 3 

 ffa 



o 



23 



29 



7 



13 



a 



3 



a 1 



m 



1 







 10 

 10 







no 

 no 



'0 

















 10 

 10 



10 

 10 



10 

 10 

 10 

 10 

 



6 

 6 



27 

 6 



6 

 6 

 6 

 6 



61.00 



?, 



Arsenate of lead powder, 1^-50 + kerosene emulsion, 10 per cent. 

 Arsenite of zinc powder, 1J— 50+ kerosene emusion, 10 per cent. 

 Arsenate of calcium, commercial powder, 1J-50+ kerosene 



0.36 



3 









0.20 



4 



3 



6 



1 



13.50 



S 





0.01 



6 



Arsenate of lead powder, 1J-50+ anthracene emulsion, 10 per 









0.01 



7 











0.14 



8 





10 

 10 

 









0.04 



9 











0.48 



in 

















53.00 









1 Foliage badly burned— unfit for consumption. 



Kerosene emulsion alone, at a 10 per cent strength, had no poison- 

 ous effect upon the fall webworm larvae — at least none had been 

 killed after having fed for a period of 27 days, with a consumption 

 of 61 square inches of foliage. The arsenate of lead alone killed the 

 10 larvae in 6 days — foliage consumed, 0.14 square inch. A com- 

 bination of these insecticides also caused the death of all the larvae 

 in 6 days after 0.36 square inch of foliage had been eaten. The 

 other arsenicals, alone or combined with the emulsion (except arse- 

 nate of calcium combined), likewise killed in 6 days after a relatively 

 small amount of foliage had been consumed. Arsenate of calcium 

 powder, used alone, was quite as effective as the other arsenicals, but 

 in combination with the emulsion 27 days were required to kill the 

 larvae, which consumed 13.50 square inches of foliage. A similar re- 

 sult was obtained in a later experiment. (See Experiment XIII.) 

 Anthracene emulsion, 10 per cent, alone and combined with arsenate 

 of lead, burned the foliage badly, rendering it unpalatable. 



As shown in Experiment XV, kerosene emulsion, 10 per cent, com- 

 bined with arsenate of lead is also an effective aphidicide. Although 

 there is some breaking down of the materials in combination, no 

 injury to the foliage was noted in the laboratory tests. 



